Dirty Air Filter: How It Will Kill Your Home’s Air Conditioner

May 12, 2013

Can’t remember to change your home’s air conditioner’s filter every 1-3 months?

It’s easy to forget because it’s not high on your priority list.
 
However, several Kansas City area homeowners have learned the hard way—leaving a dirty air filter in their cooling system too long can:

  • Reduce the volume of air coming out your supply vents, leaving you scorching hot during summer 
  • Increase your utility bills
  • Destroy the compressor (a part that costs an arm and leg to replace)

Whoa, right? We hate it when homeowners have to pay for such a small mistake. So we want to ingrain into your memory how important it is to change the filter.
 
In this article we’ll show you: 

  • How a dirty air filter can cause all these costly problems 
  • How often you should REALLY change your air filter
  • How to shop for air filters that can combat asthma and allergies

3 killer effects of not replacing a dirty air filter

So all that stuff we mentioned above sounds serious. But how does a dirty filter cause all that? Let’s focus on each one at a time.
 
Blocked airflow=little comfort
When the air filter catches as much dirt as it can, it becomes a barrier that blocks airflow. That means less air will come out your supply vents, making you less comfortable.
 
Oh, but that’s not all. Because of the restricted airflow, the evaporator coil (the part that carries cold liquid refrigerant) can frost over, reducing the amount of air coming out your vents even more.
 
Higher utility bills
Because of the reduced airflow mentioned above, your air conditioner will have to run longer to cool your home. So now you’re not comfortable AND you’re stuck with high utility bills.
 
Also, because the filter can’t catch anything anymore, the evaporator coil will get covered in dust and other airborne particles. This insulates the coil from the air, reducing its efficiency even further.
 
A destroyed compressor
The compressor is the mechanical heart of your central air conditioning system. So, in a sense, a dirty air filter can cause your air conditioner to have a “heart attack.” 
 
Here’s how. 
 
Remember when we said a dirty filter can cause the evaporator coil to freeze? Well, when that coil freezes, liquid refrigerant can flow back to the compressor (this is called “liquid slugging”).
 
This is bad news because the compressor is designed to compress refrigerant in GAS form. If the liquid refrigerant can’t leave quickly, the compressor will turn that liquid into thousands of pounds of hydraulic pressure. And something in the compressor will break— guaranteed. 
 
Oh, and it will be very expensive to fix/replace.

When to change the air filter (it depends)

OK, so you see how important it is to change the air filter. But often should you really change it? 

We said every 1-3 months at the start, but here’s a more useful rule of thumb:

  • During heavy heating and cooling months: Check the air filter once a month
  • During light heating and cooling months: Check the air filter every 3 months 

And here’s the key – change it when it looks dirty. If you can see dirt on it, it likely needs to be changed.

Need new air filters? There’s a guide for that

Most homeowners just buy the same air filter they had before.

But if you’re curious about air filters that can help clean your air to help those with asthma and allergies, check out our article: Home Air Filters: A Simple Buyer’s Guide.


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